It wasn’t a strong serve, spinning harmlessly into the middle of the box at just 82 mph; but the ball landed safely in play, and that in itself was a victory.
Coco Gauff’s serve has been under a microscope this summer. The 2023 US Open champion is unquestionably one of the best in the game, ranked third in the world and already a two-time major champion—at just 21 years old. She covers the court perhaps better than anyone in women’s tennis and boasts an all-time backhand.
But lately her serve has proved Gauff’s undoing. Gauff entered the 2025 US Open with 320 double faults on the season, 95 more than second-place Alycia Parks, per WTA stats. In fairness, Gauff has played 48 matches this season, 10th most on tour, and balances those double faults with an impressive 128 aces.
Still, as tennis problems go, a broken serve can be an existential issue. In looking to address it, Gauff, wisely, chose to take the long view.
For all she’s accomplished, the Florida native is still early in her career and wants a serve that is sustainable—even excellent. So, rather than gutting out the season with a suboptimal offering, she sought out the best in the business: biomechanics specialist Gavin MacMillan, who previously worked with Aryna Sabalenka, leading the defending US Open champion to the top of the women’s game.
“It's like learning a new language, honestly,” Gauff said of overhauling her serve. “Even looking at tagged posts of me and Gavin sending each other things back and forth, it’s like, ‘Oh, this picture looks good. This one doesn't look as good.’
“I think for me, I'm trying to not become as obsessed with it, but it is a bit because I know that this is the part of my game that needs to improve if I want to get the results that I want to achieve.”
The tennis-watching public got its first look at Gauff’s new delivery Tuesday night in Arthur Ashe Stadium, when Gauff faced Australia’s Ajla Tomljanovic in the last women’s match of the opening round. And with all eyes on her, Gauff rolled in that 82-mph spinner, and Tomljanovic promptly hit it long to give Gauff the first point of the evening.
Gauff would lose the game, but she held every other service game en route to winning the first set, and she finished the match with 10 double faults—a relatively high number perhaps, but only three more than Tomljanovic, and a reasonable total in a match that featured 17 Gauff service games and 101 Gauff service points.
“I'm someone that I'm not making any excuses,” Gauff said after outlasting Tomljanovic in a barnburner, 6-4, 6-7(2), 7-5, to advance to the second round. “It's not a mental thing. It's a biomechanical thing that I had wrong, and I'm just trying my best to get it right.”
Normally, a player would take a prolonged break to execute such a change, but Gauff decided not to wait, even if that meant making the change right before arguably the biggest tournament of the year.
“I know when I did this, I was not going to maybe serve the best, but I don't know—I just felt like I don't want to waste any more time,” Gauff said. “If I could have worked with Gavin earlier, I would have, but obviously he was on the team of another player. Then he magically became available. I knew I had to make a quick decision because I knew he would be pretty sought out after. This was what it was. I think hopefully this time next year I'll be serving much better.”
Predictably, for someone who had only been practicing with a new serve for only a week, it was a mixed bag of an evening. Gauff offset those 10 double faults with four aces, and her overall serve stats were solid if unspectacular: She made 61% of her first serves and won 66% of her first-serve points. She also won 44% of her second-serve points, a solid number against a big hitter like Tomljanovic.
Gauff was broken six times and held on 11 occasions—one each at the biggest moments. Serving up 5-4 in the third set, Gauff committed just her second double fault of the stanza to start the game, followed immediately by her third. That gave Tomljanovic the early advantage she needed to secure the match-tying break.
But even when her serve struggles, the rest of Gauff’s game remains impressive, particularly her backhand, which she backs up by covering the court as well as anyone in tennis. She wielded those weapons to break Tomljanovic to go up 6-5, and this time her serve held up, giving her the opportunity to close out the match with a spectacular running backhand winner.
“The practice week was tough because I was spending a lot of time on court literally serving until my shoulder was hurting,” Gauff said. “It's just tough. I feel like it's in the right direction, and I think for me it's trying not to go back to old habits in those tighter moments, and I think I did that today, especially in the third set.”
Therein lies the rub: In a neutral rally, Gauff is as dangerous as any player in tennis. And if she could develop her serve into a weapon—she has the ability to blast it at speeds that rival the best in the women’s game—Gauff could raise her game to heights no other woman can match.
Gauff’s next opportunity will come Thursday when she faces Donna Vekic, the 2024 Olympic silver medalist, 2024 Wimbledon semifinalist and 2019 US Open quarterfinalist. It’s another stern test for the American hopeful, who once again won’t have the opportunity to ease her serve into the tournament.
In her press conference after her first-round win, Gauff sounded like a player ready for the challenge.
“I think it's all mechanics. The approach is the approach,” she said after her victory over Tomljanovic. “I mean, people have told me certain things. Now it actually makes sense. Now it's just really trusting that new motion in those moments. … When I do it well, or when I do it, it's always a good result. It's just reminding myself how to do it.
“But, obviously, there are so many things going on in my head at those tough moments. And not just thinking about the serve. I'm thinking about how to play out the point, where to serve, what she's going to do. It's tough, but I think for me I just have to remember how I felt in the moments today and try to use that in the next match.”
